Make sure your veal shanks have twine tied around them so they don't fall apart while braising. (If they didn't come with twine, tie it on securely now.)
Heat oven to 350°.
Salt and pepper both sides of veal shanks and dredge them through the flour in a dish.
Heat 3 Tbsps olive oil in a Dutch oven on the stove top.
Add the veal shanks in one layer and brown them over high heat about 3 minutes per side. Transfer veal to a platter.
Lightly wipe residue out of the pan but make sure to leave any browned bits on the bottom. Heat the butter and remaining tablespoon olive oil over medium heat.
Add the onion, celery, carrots and oregano. Cook about 15 minutes.
While vegetables are cooking, drain the tomatoes, reserving the juice. Roughly chop the whole canned tomatoes.
Increase the heat to medium high and add the wine. Scrape up the browned bits from the bottom of pot. Cook 3-5 minutes until wine has reduced to ¼ cup. Stir in the tomato paste.
Return the veal shanks to the pot.
Add the tomatoes, tomato juice, broth, thyme, bay leaf.
Add ½ teaspoon salt and ½ teaspoon pepper.
Increase heat and bring the sauce to a boil. Cover tightly with foil or lid and transfer Dutch oven to the oven.
Braise for 1 ½ hours. Check mid way to see ifyou need to add more broth. Liquid should come halfway up the side of the shanks. Add more broth as needed.
Remove Dutch oven and check veal for tenderness. The meat sections should be pulling part or separate easily with a fork. Cook another ½ hour if needed.
When veal is tender, carefully transfer shanks to a plaater with a spatula so they don't fall apart completely.
Strain the vegetable mixture and reserve the juice. Press on the vegetables to maximize juice quantity. (Hint - don't throw away those delicious braised vegetables. Add broth to them separately, remove the bay leaf and serve as a delicious soup.)
Return the juices to the Dutch oven. Dissolve the cornstarch by shaking it in a jar with ¼ cup of the juices. Whisk the cornstarch slurry in to the juices and simmer to thicken the sauce. Return shanks to the pot.
At this point you can mix up the Gremolata, add it to the pot, remove the twine from the shanks and serve.
If making ahead you can cool the Dutch oven and refrigerate overnight. Reheat the veal and sauce in a 350° degree oven for 35 minutes. Mix up the Gremolata and stir it in to the sauce just before serving.